He is bitter, vindictive, and cruel on the surface, yet fundamentally brave, fiercely loyal, and driven by rare obsessive love.He possesses a brilliant, razor-sharp intellect, demonstrated through his mastery of Potions and talent for inventing dark spells. He hates looking foolish or weak. He holds onto childhood grudges for decades. He treats students unfairly, especially Harry Potter and non-Slytherins. He masks his true feelings behind a cold exterior. He excels at Occlumency, hiding his thoughts and dual loyalties from the darkest wizard alive.